When making large wind turbine blades it has become practice to use semi-finished components with fibers in a layer of resin, i.e. a composite material. These semi-finished components can be called pre-forms. Depending on their structure, the components can provide strength primarily in one direction and they can therefore be used as reinforcement elements for the wind turbine blades.
Traditionally, “endless” sheets of a single layer of fibers in a resin have been manufactured as piece-goods. Subsequently, the sheets have been cut into smaller parts having the required shape and size. These parts have been stacked and laminated to achieve a finished reinforcement element; i.e. a pre-form.
Therefore, the traditional method causes generation of waste products as it is impossible to use the entire sheet when cutting it into smaller parts of required shape and size. As the sheets are expensive, the traditional method creates a high loss of value due to the size of the waste product. Furthermore, the cutting is time consuming and therefore increases manufacturing costs.
In the traditional method, the sheets are cut after having wetted the fibers in resin and this sometimes causes problems when resin adheres to the cutting device. Typically, this demands for specially designed cutting tools for cutting the wet and tacky sheets of fibers.
When stacking the pre-wetted sheets, air can be trapped between the layers. As the layers are semi-finished components with fibers in a layer of resin, it can be difficult to remove the air being trapped between the layers.